The present invention relates to an improved process for the continuous simultaneous production of dihydroxybenzene (DHB) and diisopropylbenzene dicarbinol (DCL) from diisopropylbenzene. More specifically, this process includes the steps of: oxidizing diisopropylbenzene to obtain an oxidate comprising, among other things, diisopropylbenzene dihydroperoxide (DBP) and diisopropylbenzene hydroxyhydroperoxide (HHP); extracting DHP and HHP from the oxidate into an aqueous caustic solution using a Karr Column operation; continuously and simultaneously isolating HHP and DHP into separate fractions from the caustic solution by using Karr Column cold and hot methyl isobutyl ketone (MIBK) extractions; producing dihydroxybenzene by the cleavage of the DHP extract fraction in the presence of an acid catalyst; and producing dicarbinol by decomposing the HHP fraction under atmospheric conditions using an aqueous alkaline solution.
It is known in the art that hydroperoxides, such as diisopropylbenzene dihydroperoxide (DHP), diisopropylbenzene monohydroperoxide (MHP), and diisopropylbenzene hydroxyhydroperoxide (HHP), can be produced by oxidizing diisopropylbenzenes with molecular oxygen either in the presence or absence of base catalysts. The continuous oxidation and production of diisopropylbenzene dihydroperoxide from the diisopropylbenzenes in the presence of a strong base, such as sodium hydroxide, are disclosed, for example, in British Patent No. 727,498 and U.S. Pat. No. 3,953, 521. These patents disclose that m- and p-diisopropylbenzene dihydroperoxides can be continuously isolated from the diisopropylbenzene oxidation mixture by caustic extraction, and that continuous oxidation of diisopropylbenzenes for the production of dihydroperoxides can be achieved by maintaining the pH in a range of between 8 and 11 and the temperature at about 85-95xc2x0 C. in the oxidation reactor. British Patent No. 727,498, as well as U.S. Pat. No. 2,856,432, also disclose that the dihydroperoxides (DHP) present in the diisopropylbenzene oxidation mixture can be effectively separated by means of 4-8 wt. % caustic solutions. In addition to dihydroperoxide (DHP), part of the hydroxyhydroperoxide (HHP) present in the oxidation material is also extracted into the caustic solution.
U.S. Pat. No. 4,237,319 also discloses a method for the batch production of m-diisopropylbenzene dihydroperoxide (m-DHP) by oxidizing m-diisopropylbenzene under alkaline conditions.
Extraction of DBP into the caustic solution, as described in the above art, can be followed by isolation of the DHP for the production of a dihydric phenol, such as resorcinol or hydroquinone, in several ways. Of these methods, a preferred method in the art is to extract the DHP from the caustic solution into an organic solvent, preferably MIBK. Using this solvent, a temperature of 70-80xc2x0 C. and contact times of 5-10 minutes, it is possible to extract a high proportion of the DHP into MIBK with negligible losses by decomposition. British Patent No. 921,557 discloses that m-DHP present in the aqueous caustic solution is extracted by the MIBK solvent at 75xc2x0 C. In order to improve the extraction efficiency, U.S. Pat. No. 3,932,528 discloses that by adding about 1% ammonia into an aqueous 8% caustic soda solution containing 12.3% DHP, MIBK solvent is more effective at 60xc2x0 C. for DHP extraction through three counter-current contact stages.
U.S. Pat. No. 4,059,637 describes a method by which DHP present in the caustic solution is extracted using MIBK solvent in a four-stage countercurrent mixer settler-type extraction. The caustic solution containing DHP used in the mixer settler-type extraction is previously treated with MIBK at a temperature of below 30xc2x0 C. to remove oxidation by-products having 2-hydroxy-2-propyl group such as diisopropylbenzene hydroxyhydroperoxide (HHP) and diisopropylbenzene dicarbinol (DCL). The HHP content of the caustic solution containing DHP prior to feed into the mixer-settler extraction is reported to be about 4.2%. After the extraction, the purity of DHP in the MIBK solution is reported to be 93%.
Several patents disclose different acid type catalysts and temperatures to obtain a dihydric phenol such as resorcinol or hydroquinone from the DHP by cleavage. For example, British Patent No. 743,736 discloses sulfuric acid as the catalyst for m-DHP cleavage in the presence of an MIBK solvent under reflux conditions. With a residence time of between about 7.5-10 minutes and a 0.2 wt. % H2SO4 catalyst, 99.6% of the DHP is decomposed. British Patent No. 819,450 discloses a sulfur trioxide catalyst for the cleavage of m-DHP; sulfur trioxide is reported as causing a far more rapid cleavage reaction than the corresponding quantity of sulfuric acid. The decomposition of m-DHP is carried out continuously in two reactors connected in series, using MIBK and acetone as the solvents employed in the cleavage operation. Canadian Patent No. 586,534 also discloses the use of a sulfur trioxide catalyst for cleaving m-DHP in the presence of 0.3 wt. % water in the cleavage reaction. U.S. Pat. No. 3,923,908 discloses a process for cleaving diisopropylbenzene dihydroperoxides in the presence of impurities such as isopropylphenyl dimethylcarbinol (MCL), diisopropylbenzene hydroxyhydroperoxide (HHP) and diisopropylbenzene dicarbinol (DCL) using a sulfur trioxide catalyst and a solvent.
In order to effectively utilize the by-product diisopropylbenzene hydroxyhydroperoxide (HHP), Japanese Patent Application 95-304027 and Japanese Patent Application No. 95-301055 disclose a method by which an MIBK solution containing HHP is reduced by hydrogen in the presence of a palladium-alumina catalyst (a material carrying 1 wt. % of palladium metal) in an autoclave equipped with an agitator, at a hydrogen pressure of 6 atmospheres and a reaction temperature of 90xc2x0 C., to obtain diisopropylbenzene dicarbinol (DCL). Though this method produces DCL from HHP, the safety of this process is questionable, as it involves handling high pressure hydrogen in the presence of a highly volatile solvent (MIBK) at high temperatures.
One important aspect recognized in the art of producing high purity dihydric phenol by the hydroperoxidation technology is to prepare a high purity cleavage feed (DHP) from the diisopropylbenzene oxidation mixture. Although DHP is produced in the DIPB oxidation, it may not be easy to completely remove the DHP from the oxidation mixture for use in the cleavage step of the hydroperoxidation process. In a standard first step of DHP separation from the oxidate, caustic extraction is typically performed using either a 4% or 8% NaOH solution. During this extraction, DHP as well as other impurities present in the oxidate, such as HHP, acetyl-isopropylbenzene hydroperoxide (KHP), MHP, etc., are extracted. When an 8% NaOH solution is used, about 90-95% of the HHP and KHP present in the oxidation mixture are known to be extracted into the caustic solution, along with about 1-2% MHP. MHP present in the caustic solution is back extracted with a DIPB solvent. The solution comprising the DIPB, extracted MHP and other extracted oxidation impurities can then be recycled to the oxidation reaction and subjected to oxidation. This DIPB extraction does not have much effect on removing other impurities such as HHP and KHP from the caustic extract solution, however. To remove the HHP from the caustic solution, an MIBK solvent extraction is typically done at a low temperature. In spite of this operation, the concentration of HHP in the caustic solution before the final MIBK extraction can still be relatively high and, therefore, this method has been found to be a difficult route to produce a very high purity DHP for the cleavage. None of the patents or other literature in the art suggest or disclose what happens to impurities such as KHP present in the caustic extract. If the extraction procedures or methods are not efficient, then the hydroperoxidation process impurities are expected to interfere with the isolation of a very high purity DHP needed for a highly efficient cleavage operation. None of the art teaches or suggests a process by which, in a continuous operation, a very high purity DHP can be produced from the diisopropylbenzene oxidation materials.
In an attempt to make a high purity DHP material, U.S. Pat. No. 4,059,637 describes a method in which four mixer-settler type extractors are used. The DHP-containing caustic solution used in the ""637 patent contained DHP and HHP in a ratio of about 95.8:4.2, even after the MIBK extraction was performed at 20xc2x0 C. on the solution. According to this patent, this cold MIBK extraction of the caustic extraction was done separately as a discontinuous process rather than being integrated with the mixer-settler extraction operation. This procedure produced a low purity DHP-containing product for the cleavage reaction.
Thus, the techniques used in the art to separate a high purity DHP from the DIPB oxidation materials have disadvantages. No single process completely describes a continuous method of obtaining a high purity DHP from the oxidate, while identifying and characterizing the nature of impurities extracted into the caustic and MIBK extractions. In addition, art-described methods for preparing DCL from DIPB oxidation materials give rise to safety concerns. There remains a need, therefore, for such a process which provides for the safe and efficient preparation of products such as a high purity DHP feed for use in preparation of DHB, as well as DCL.
The present invention has met the above described needs by providing a novel process for the preparation of a dihydric phenol, such as resorcinol or hydroquinone, from a high purity DHP-containing cleavage feed while also effectively utilizing the HIP impurity in the oxidation product of DIPB for the manufacture of dicarbinol. This method generally comprises the steps of oxidizing diisopropylbenzenes with molecular oxygen in the presence of a base catalyst to obtain an oxidation reaction mixture, also referred to herein as xe2x80x9coxidatexe2x80x9d, comprising, among other things, diisopropylbenzene dihydroperoxide (DHP) and diisopropylbenzene hydroxyhydroperoxide (HHP); feeding the oxidate into a Karr Column, also referred to herein as a xe2x80x9ccaustic extraction columnxe2x80x9d; continuously and simultaneously extracting DHP and HHP from the oxidate in a counter-current operation; continuously generating a DHP/HHP enriched caustic, also referred to herein as xe2x80x9crich causticxe2x80x9d, and a recycle stream, which recycle stream can be directly fed back into the oxidation reactor; continuously feeding the rich caustic into a second Karr Column, also referred to herein as xe2x80x9ccold MIBK columnxe2x80x9d, for the simultaneous and continuous generation of DHP enriched caustic and the separation of HHP from the DHP enriched caustic achieved by performing this MIBK extraction operation at a low temperature, also referred to herein as xe2x80x9ccold MIBK extractionxe2x80x9d; continuously feeding the DHP enriched caustic into a third Karr Column, also referred to herein as xe2x80x9chot MIBK columnxe2x80x9d, for the continuous generation of a very high purity DHP to obtain an MIBK solution, herein referred to as xe2x80x9chot MIBK solutionxe2x80x9d, for feeding to a cleavage step for continuous generation of dihydroxybenzene and continuous generation of a lean caustic containing very low levels of unextracted hydroperoxides. Prior to cleavage, the hot MIBK solution is preferably concentrated; the concentrate is then fed into a continuous cleavage reactor where DHP is cleaved in the presence of a catalyst to produce the corresponding dihydric phenol, such as resorcinol or hydroquinone, and acetone. The HHP present in the cold MIBK extract obtained following the second Karr Column extraction is decomposed by treatment with an aqueous alkaline solution under atmospheric and aqueous conditions to obtain the corresponding dicarbinol.
It is, therefore, an object of the present invention to provide an improved process for the production of polyphenols, such as resorcinol or hydroquinone, and dicarbinol from diisopropylbenzenes.
A further object of the present invention is to provide a process for the continuous separation of DHP from the DIPB oxidation material and generation of an oxidation recycle feed and a rich caustic stream from the caustic extraction using Karr Column operations.
A further object of the present invention is to provide a process for the continuous and highly efficient separation of the impurities such as HHP, KHP, MHP, and other oxidation impurities from the DHP/HHP rich caustic stream by performing a cold temperature MIBK extraction in a Karr Column.
Another object of the invention is to provide a process for production of a DHP enriched caustic for high temperature MIBK extraction in a Karr Column.
Another object of the present invention is to provide a process for the continuous production of a very high purity DHP material feed for the cleavage step of the hydroperoxidation process by performing MIBK extractions on the caustic extract solution using Karr Column operations.
Still a further objective of this invention is to provide an aqueous, nonhydrogenated, safe, effective and efficient process for the conversion of HHP to DCL.
These and other objects of the invention will be apparent from the following description of the invention.